One molecule, many atoms: Platinum bonds respond to surface features up to 10 nanometers away
Many chemical processes that sustain modern society depend on molecules binding to metal surfaces. The production of synthetic fertilizer, for example, relies on heterogeneous catalysis, in which gases react on the surface of a solid catalyst. Yet, until now, an important question has remained unresolved: How much of the metal surface actually participates in determining the strength of a…
A molecule can form a bond with a metal surface through interactions with atoms that are many nanometers away, according to a study by researchers from the Max Planck Institute for Multidisciplinary Sciences and the Center for Quantum Nanoscience. The findings, published in Science, challenge the traditional view of chemical bonding as a local interaction.
Using platinum surfaces with regularly spaced atomic steps, the researchers discovered that moving a neighboring step up to 10 nanometers away could alter the strength of a molecule's bond at a given step, by up to 0.2 electron volts. The extent of this effect varied depending on the type of molecule - 7 nanometers for ammonia, 6 nanometers for carbon monoxide, and 4 nanometers for nitric oxide.
The team developed a new model that combines molecular orbital theory with electronic band structure, revealing that different molecules interact with different electronic states in the metal. This electronic connectivity explains why the bond strength can be influenced by structural variations on the surface, even when the influencing feature is many atomic spacings away.
The study suggests that models of catalytic activity based solely on the local arrangement of atoms around an adsorption site may not fully capture the behavior of catalysts made of metals with strongly delocalized electronic bands, such as platinum. The findings highlight the importance of considering how the surrounding solid modifies the electronic states involved in bonding, particularly for nanoscale catalysts.
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